Despite my background in geology, like many others I used to picture tsunamis as large versions of standard waves- you know, with the curl and break and so on. It was the swarm of videos that came out in the aftermath of the 2004 Boxing Day Earthquake in Sumatra, Indonesia that really clarified what happened. It seems more accurate to me to describe them as temporary changes in sea level with an amplitude on the order of meters to tens of meters, and a duration of minutes or longer. They are waves, of course, but the effect is that the sea level just comes up and up. And up.
The NYT has just published a video clip of the recent tsunami in Chile that illustrates this well. This was stressful for me to watch; that poor yapping dog trying to balance on the fence from the beginning of the clip is still clinging to the fence at the end... so I'm guessing it survived. I was also relieved to not see any human victims, though of course in reality there are hundreds dead as the result of this tsunami.
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